Our laboratory has long been interested in the mechanisms by which lung injury increases pulmonary vascular pressure and fluid conductance. This research proposal will investigate the roles of cyclic nucleotides, lipoxygenase and cyclooxygenase arachidonic acid (AA) products, and free radicals in the pathophysiology of lung injury. Three clinically relevant injury models will be studied: oxidant, HC1 instillation and endotoxin. Measurements will include lung weight, pulmonary arterial, left atrial, and tracheal pressures, and alveolar-capillary or endothelial permeability to 99MTc labeled OPTA (MW 497) and FITC labeled dextran (MW 7000). We will measure by RIA and HPLC the perfusate concentrations of thromboxane and prostacyclin metabolites, and leukotrienes B4 and C4/D4. The first specific aim evaluates the importance of changes in cAMP in lung injury. This proposal will test the hypothesis than an increase in cAMP will antagonize the vascular effects of lung injury by preventing endothelial cell contraction and that fluid conductance varies inversely with cAMP levels. This proposal will also study the effects of cGMP, beta agonists, and alpha agonists on baseline pressure and fluid conductance. We will also morphologically measure contraction of cultured endothelial cells during oxidant challenge and determine if increased cAMP can prevent these changes. The second aim will test the hypothesis that in the 3 lung injury models AA mediators greatly contribute to the pulmonary edema produced. The proposal will test the hypothesis that the leukotrienes account for the increased permeability in these models. We will also measure AA mediator production by cultured endothelial cells and determine if AA mediators can change cell morphology, permeability and cAMP level. Experiments will determine the effect of H+ and PO2 on production and function of AA metabolites. The third aim will determine the importance of free radical generation in acute lung injury. We will use unenhanced low level chemiluminescence as a measure of singlet 02 production and lucigenin enhanced chemiluminescence to measure superoxide anion production. We will also use two fairly specific free radical scavengers for singlet 02 od hydroxyl radical. Using these probes we investigate the role of superoxide anion, singlet 02 and hydroxyl radical in lung injury and to determine if free radicals produced by the AA metabolic pathway are biologically important. The results of these experiments may lead to the development of a more rational treatment of acute lung injury in man.